Arc converter



Nov. 2 1926.

P. O. PEDERSEN ARC CONVERTER original Filed June 21, 1919 N ZJN N m owm m m m. H Y B W/ TNESSES flaw %;M.

Patented Nov. 2, 1926.

UNITED STATES 1,6t5,07 PATENT QFFECE.

PEDEB. O. PEDERSEN, OF FREDEEIKSBERG, DENMARK, ASSIGNOR TO IOULSEN WIRE- LESS CORPORATION, A CORPORATION OF ARIZONA.

ARC CONVERTER.

Original application filed. June 21, 1919, Serial No. 305,844, and in Denmark March 4, 1919. Patent No. 1,544,102, dated June 30, 1925. Divided and this application filed December 1, 1923. Serial No.

This invention relates to an arc converter for producing high frequency oscillations in an electric circuit, and more partcularly to the so-called Poulsen are.

The use of such arcs fed from a low frequency source to produce high frequency oscillations is now well-known; in such de vices a magnetic blowout is provided for extinguishing the arc during each cycle of high frequency, the oscillations being produced by the rapid variations in arc length and resistance.

This application is a division of a prior application filed in my name, entitled Arc generators, having Serial No. 305,844, and filed June 21, 1919, Patent No. 1,544,102, dated June 30, 1925.

It is one of the objects of my invention to increase the stability of an arc converter of the Poulsen type.

In order to secure best results with an arc converter, the magnetic field that influences thearc should be just strong enough to blow out the are once in each cycle. In case the magnetic field be materially weaker than this desired value, the arc will have a tendency to travel too far along the electrodes and away from the edges; this results in a reduced efliciency owing to the existence of an unnecessarily high are voltage corresponding to this period, and furthermore the frequency of operation will also vary. But even with the most favorable value of the magnetic field to produce the desired extinction voltage, there is a gradual increase in arc resistance following the comparatively gradual rise of the extinction voltage, so that the efliciency of the are is limited.

It is another object of my invention to overcome this effect as much as possible, by ensuring that there be little variation in resistance from the time of drawing to the time of extinction of the arc. Stating it in another way, the object is to reform the conditions of starting and blowing-out of the. arc, whereby the are resistance is reduced to a favorable minimum while the arc is burning. According to the invention this is accomplished by providing the cathode with cooling or other means which limits the outward travel of the arc, and regulates the temperature at the starting point for a desired high starting voltage. It is also point-- ed out in this application how the electrodes may be formed, or arranged, or formed and arranged, relatively to each other, to augment this increase in efficiency, by reducing to favorable values, the increase in length and resistance of the arc during its period of burning in each cycle.

My invention possesses other advantageous features, some of which with the foregoing will be set forth at length in the following description, where I shall outline in full those forms of the invention which I have selected for illustration in the drawings accompanying and forming part of the present specification. Although I have shown in the drawings only a few embodiments of my invention, I do not desire to be limited there to, since the invention as expressed in the claims may be embodied in other forms also.

Referring to the drawings:

Figure 1 shows for comparison the usual arrangement of the electrodes of an arc converter;

Fig. 2 shows one embodiment of my invention; and

Fig. 3 shows a modification.

In the prior arrangements as illustrated in Fig. 1, the anode 1, which is shown as water cooled, is placed directly opposite a cathode 2. lVhen the arc ignites it forms the path 3, and it is then gradually bowed out and increased in length until it is ex tinguished in the position 4. There is no limit placed on the travel of the arc, and it is possible that with a slightly inaccurate adjustment of the field, the arc may be eX- tinguishe-d only after it has been drawn out to an undesirable extent.

In Fig. 2 such an occurrence is obviated, since there is a physical limit to the point of travel of the arc. This is accomplished by providing a cathode 5 having a cooling back piece 6. This piece is formed of a poor electrical conductor, such as resistance carbon or a resistance metal having a high melting point. As soon as the arc strikes this back piece, a high resistance is introduced thereby into the circuit, the current through the are decreases, and there is an attendant drop in the are temperature, causing the arc to be extinguished. The back piece 6 may be joined to the cathode 5 or not, as-desired.

In this modification, therefore, there is a limit to the extent of arc length increase, and consequently the arc resistance is also limited, and maintained as near to its practicable lower limit as feasible, during the entire time of burning.

Substantially the same results may be obtained in other ways; for example in Fig. 3 there is shown an anode 7 of the usual form, and a cathode S, which is provided with a shoulder 9. This shoulder is made abrupt a d fairly large in extent, so that the are between the electrodes cannot extend further than they position shown at 9. The length of catho. e 8 is accordingly chosen to correspond substantially exactly with the desired travel of the are, which is blown out at the hindmost edge or shoulder 9.

In both of the embodiments of Figs. 2 and 3, the cathode length must be determined with due regard to the limitation ot' the arc travel. The embodiments diller however in the mode of preventing the are from travelling turtherthan defined by the cathode. In Fig. 2 this is accomplished by a cooling eil'ect due to reduced current flow upon leaving the cathode; while in Fig. 3 the same eiiect is produced by so formingthe cathode physically that it is substantially impossible tor the arc to spread beyond a definite point.

I claim:

1.. In an arc converter, a cathode having a length just equal to the most tavorable distance of travel of the are along the cathode.

2. In an arc converter, a cathode, and a back piece for the cathode made from a material having materially poorer conductng properties than the cathode.

3. In an arc converter, a pair of electrodes between which an arc is to be formed, one of said electrodes having a length just equal to the most favorable distance of travel of the are along the cathode.

4t. In an arc converter, a pair of electrodes between which an arc is to be formed, and a back piece for one of said electrodes mace from a material having materially poorer conducting properties than its asso ciated electrode.

In an arc converter, a pair of electrodes between which the arc is formed, means tor influencing the are by a magnetic field, whereby the are travels along the electrodes between the time of drawing and extinction, and means for lin'iiting the travel of the are along the electrodes, comprising a resistance element disposed back of one of the electrodes and in the path of travel of the are.

6. In an arc converter, a pair of electrodes between which the are is formed, means for influencing the are by a magnetic field, whereby the arc travels along the electrodes between the time of drawing and extinction, and means whereby a resistance is intro duced in the arc circuit upon travel of the are beyond a definite limit.

In testimony whereof, I have hereunto set my hand.

PEDEB O. PEDERSEN. 

